1. Field of the Invention
The present invention relates to a digital camera and a method of controlling the same.
2. Description of the Background Art
In digital cameras having a zoom lens, the focal distance of the zoom lens can be continuously changed by moving the zoom lens. When the focal distance is increased, an image formed on an imaging surface is made large, thereby obtaining a telephotographic effect. When the focal distance is decreased, the image formed on the imaging surface is made small, thereby making wide-angle imaging possible.
A single-lens reflex camera, for example, of cameras having a zoom lens can employ such a lens structure that the f-stop value of the zoom lens is not changed even if the focal distance thereof is changed. However, a small-sized camera having a zoom lens employs such a lens structure that the f-stop value of the zoom lens is increased if the focal distance thereof is increased because it is generally difficult to employ such a lens structure that the f-stop value of the zoom lens is not changed even if the focal distance thereof is changed. In the small-sized camera, therefore, a subject image obtained in a state where the focal distance is long is liable to be darker, as compared with a subject image obtained in a state where the focal distance is short. That is, the f-stop value is increased when the focal distance is increased. Therefore, a subject image obtained in a state where the focal distance is long is darker, as compared with a subject image obtained in a state where the focal distance is short.
As lighting for obtaining a subject image having sufficient brightness in an environment whose surroundings are dark, for example, a strobe using a xenon tube is typically used. Further, in the case of a digital camera, an image signal obtained by imaging a subject is amplified using an amplifier to brighten an obtained subject image. When in the small-sized digital camera having a zoom lens, the imaging signal is amplified depending on only the f-stop value and the focal distance of the zoom lens, however, the image signal may be amplified by the amplifier irrespective of the fact that sufficient brightness is obtained by only light from a strobe. The amplification of the image signal by the amplifier brightens the subject image and mixes noise components into the obtained image signal, to degrade the image quality. It is preferable that the image signal is unnecessarily amplified as little as possible by the amplifier.